In conventional alloying of metal ribbon, filaments, fiber, or film it is often difficult to obtain and/or maintain a uniform mixture of molten alloy material across the exit or pouring lip of a pouring vessel onto the surface of a heat-extracting substrate. This difficulty is due to, among other factors, non-uniform cooling of the metal or metals in various parts of the pouring vessel, or to non-uniform mixing of the metals in the formation of the molten alloy material, or to non-uniform velocity of the molten alloy material as it flows through the pouring vessel toward the pouring lip.
Various systems have been employed to attempt to avoid these problems. For example, U.S. Pat. No. 4,678,719, issued on July 7, 1987 to Johns et al. and assigned to Allegheny Ludlum Corporation, teaches a widening tundish in an attempt to control the velocity profile of the flow of molten material to thereby aid strip casting of crystalline metal. However, additional baffles and weirs are needed to further control the velocity profile toward the cooling substrate and/or to control the depth across the width of the tundish. Furthermore, the design of Johns et al. provides only laminar flow or direct delivery of the molten flow to the casting or cooling surface. This can result in non-uniform delivery rate across the surface of the cooling substrate. Johns et al. is not directed to alloying of molten materials.
Hackman et al., in U.S. Pat. No. 4,813,472, issued Mar. 21, 1989 teaches an improved method for producing filaments or fiber from a molten material by overflowing the molten material against the surface of a rotating cooling substrate. Hackman et al. is not directed to alloying of molten materials.
Also known are orifice-type casting systems wherein molten material is delivered from a nozzle to the quenching or casting surface. However, poor quality can result from such casting systems due to non-uniform cooling, partial shrinkage of the strip, and the development of cracks in the strip.
In addition, orifice-type extrusion systems suffer from relative complexity of the necsesary process control systems and the difficulty in passing a molten material through fixed, small orifices. The orifice must be constructed from an exotic material if the molten material has a relatively high melting point. The orifices have a tendency to erode and/or become partially or completely blocked due to the freezing of material on the orifice.
Conventional alloying processes generally require the premixing of the materials to be alloyed before the molten alloy material is poured into the tundish apparatus. In this manner, it is often difficult to achieve and maintain even distribution of one molten component in the other molten component. It is also difficult to determine whether the heavier or the higher-melting of the materials to be alloyed is still molten and/or dispersed in the lighter or lower-melting of the materials.
Thus a method and apparatus are desirable which are suitable for commercial production of metal alloy at reduced cost and with improved control of the molten alloy material flow. It is an object of the present invention to provide a method and an apparatus for improved alloying of metal strip, which method is superior to known alloying and casting processes.
Another object of the present invention is to provide a system for forming ribbon, filaments, fiber, or film metal alloy products directly from a mixture of molten alloy materials in a manner whereby the mixing is improved and the depth, cooling rate, wetting of the exit lip, and velocity of the molten alloy material flowing toward a cooling substrate are also controlled.